Handheld driving tools with propellant charges are known from the prior art, in which the combustion gases resulting after ignition of a pyrotechnic charge expand in a combustion chamber. Thereby a piston as an energy transfer means is accelerated and drives a fastener into a workpiece. The most optimized, residue-free and reproducible combustion of the charge possible is fundamentally desired. It must be taken into account in this regard that the charge generally includes particles such as powder grains, fibers or the like, which are initially driven ahead of a flame front upon ignition.
U.S. Pat. No. 6,321,968 B1 describes a driving tool having a propellant charge, in which the combustion chamber is separated by means of a perforated disk into an upper partial chamber and a lower partial chamber. Powder grains of the propellant charge are larger than the holes of the disk. Therefore the powder grains are initially accelerated in the central discharge region toward the perforated areas of the separating disk, where they are retained due to the dimensioning of the holes in the separating disk, so that the powder grains are primarily combusted in the upper partial chamber. FIG. 10 shows a variation in which a propellant charge is used without a cartridge. Due to the design of this variant, an ejection region enclosing the central axis and extending between the propellant charge and a central region of the separator disk cannot be provided in the upper partial chamber. The ejection region according to FIG. 10 therefore does not include the central axis of the combustion chamber but is instead arranged in a ring shape about a central plunger of the combustion chamber. The cartridge-free charge is ignited at an upper end of the central plunger.
U.S. Pat. No. 6,321,968 B1 also presents an adjustability of a dead space volume in order to adjustably modify the driving energy of the tool. A valve-like slide can be adjusted in a direction perpendicular to a driving axis for this purpose. Even in the closed position of the slide, the combustion chamber has a dead space, which is formed as a recess in a side wall of the combustion chamber.
The problem addressed by the invention is that of specifying a driving tool that allows an effective adjustment of a driving energy for a given propellant charge.